1. Field of the Invention
The present invention relates to an Internet protocol (IP)-private branch exchange (PBX) system and a method for linking the system with a Voice over Internet Protocol (VoIP) terminal.
2. Description of the Related Art
With the rapid development of the Internet, demand for various services has been continuously increasing. A typical example of a service in demand is a VoIP communication service.
In response to such demand, it became possible to use VoIP communication service on a legacy terminal of an extension of an IP-PBX based on IP.
However, the IP-PBX system has a problem in that it cannot use a VoIP terminal, such as an H.323 terminal and a SIP terminal, using VoIP protocol for VoIP communication service in the extension.
In other words, the IP-PBX system cannot use a VoIP terminal supporting a protocol, e.g., H.323 or SIP, standardized by a standardization organization, e.g., the International Telecommunication Union (ITU), the Internet Engineering Task Force (IETF), or the European Telecommunications Standards Institute (ETSI), for VoIP communication service in the extension of the IP-PBX.
When it comes to linking an IP-PBX system and a newly developed VoIP terminal, the inability of the IP-PBX system to work with a VoIP terminal using a standard protocol is a problem for the manufacturer or administrator of the IP-PBX system.
In addition, it is inconvenient for a user of a digital phone linked with an IP-PBX to input a prefix in addition to a phone number of an external SIP terminal in order to put a call through to the external SIP terminal.